MEMs let tiny gyro keep cars safe

Stability control and other active safety systems that deal with brakes, steering, and suspensions are based on inputs from angular-rate sensors.

Sep 27, 2007

Such sensors need to be reliable and durable enough to operate despite harsh under-the-hood conditions and temperatures up to 125C. One such sensor, the Micro- Gyro from Systron Donner Automotive, Moorpark, Calif. (systronauto. com), meets these criteria, plus it is relatively small and lightweight. It is based on a double-ended tuning fork micromachined out of pure crystalline piezoelectric quartz. The quartz remains stable over time, so the sensor’s specs don’t vary from the day it was manufactured.

Engineers minimized analog circuity and concentrated on digital ICs, which makes the sensor relatively immune from high temperatures. And continuous built-in testing monitors the gyro’s circuitry while also sensing the vehicle direction, even in high-g conditions. It outputs a fully compensated 3.3 or 5.0-V digital signal. Users can add another sensed axis to a system by adding another MicroGyro.